Responses of thoracic spinal neurons to activation and desensitization of cardiac TRPV1-containing afferents in rats

Chao Qin, Jay P. Farber, Kenneth E. Miller, Robert D. Foreman

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

The purpose of this study was to examine how upper thoracic spinal neurons responded to activation and desensitization of cardiac transient receptor potential vanilloid-1 (TRPV1)-containing afferent fibers. Extracellular potentials of single T3 spinal neurons were recorded in pentobarbital- anesthetized, paralyzed, and ventilated male rats. To activate cardiac nociceptive receptors, a catheter was placed in the pericardial sac to administer various chemicals: bradykinin (BK; 10 μg/ml, 0.2 ml), capsaicin (CAP, 10 μg/ml, 0.2 ml), or a mixture of algesic chemicals (AC; 0.2 ml) containing adenosine 10-3 M, BK, serotonin, histamine, and PGE 2, 10-5 M for each. Spinal neurons that responded to intrapericardial BK and/or CAP were used in this study. Results showed that 81% (35/43) of the neurons had excitatory responses to both intrapericardial BK and CAP, and the remainder responded to either BK or CAP. Intrapericardial resiniferatoxin (RTX) (0.2 μg/ml, 0.2 ml, 1 min), which desensitizes TRPV1-containing nerve endings, abolished excitatory responses to both BK (n = 8) and CAP (n = 7), and to AC (n = 5) but not to somatic stimuli. Intrapericardial capsazepine (1 mg/ml, 0.2 ml, 3 min), a specific antagonist of TRPV1, sharply attenuated excitatory responses to CAP in 5/5 neurons, but responses to BK in 5/5 neurons was maintained. Additionally, intrapericardial capsazepine had no significant effect on excitatory responses to AC in 3/3 neurons. These data indicated that intrapericardial BK-initiated spinal neuronal responses were linked to cardiac TRPV1-containing afferent fibers, but were not dependent on TRPV1. Intraspinal signaling for cardiac nociception was mediated through CAP-sensitive afferent fibers innervating the heart.

Original languageEnglish
Pages (from-to)R1700-R1707
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume291
Issue number6
DOIs
StatePublished - 18 Dec 2006

Keywords

  • Bradykinin
  • Capsaicin
  • Resiniferatoxin
  • Sympathetic afferent
  • Vagal afferent

Fingerprint Dive into the research topics of 'Responses of thoracic spinal neurons to activation and desensitization of cardiac TRPV1-containing afferents in rats'. Together they form a unique fingerprint.

  • Cite this